Nutritional studies often address several independent variables but do not, or are not able to, distinguish which factors lead to which outcomes. Thus, a perplexing and incomplete picture has emerged for many aspects of enteral feeding management for which nurses have responsibility. Enteral feeding is the delivery of food by tube into the stomach or small intestine. To build a necessary knowledge base for nurses to make decisions promoting optimal enteral nutrition for patients, this multiphase study will first use a well-established rat model (Phases 1 and 2), and the include human oncology patients with enteral feedings or enteral feedings plus a set of antineoplastic chemotherapy regimen as subjects (Phase 3). In the combined two animal model phases, a prospective, experimental 2x2x2x2x2, randomized post-test only design will be used to examine the effects of enteral feeding delivery times (24 and 12hr), methods (infusion and bolus), kilocalorie (kcal) levels (80 and 55), and fiber contents (high and low) on plasma corticosterone, insulin and gut integrity. Phase 2 will replicate Phase 1, with the addition of the fifth independent variable, specific antineoplastic chemotherapy regimen in the animal model to move closer to human situations in which enteral feedings are used. During the first part of each animal Phase, 5 rats will be in each cell for the two dependent variables of plasma corticosterone and gut structural integrity (=80). A second set of 80 rats will be used for the dependent variables of plasma insulin and gut functional integrity. The rats will be studied for 21 days after 7 days of environmental acclimation and surgical gastrostomy tube placement. Enteral feedings will begin on day 11. Hourly blood draws are planned for study Days 19 and 20. Ten samples of 0.2ml each will be withdrawn from each rat through a surgically implanted vascular catheter. On day 21, tissues will be harvested for gut structural or functional integrity measures. Composite integrity indexes will be generated and used in analyses. In Phase 3, a prospective, descriptive time series design has been chosen to explore systemic cortisol levels and gastrointestinal (GI) sensations experienced by a sample of oncology patients (n=20), half receiving enteral feedings, and half receiving enteral feedings plus a specified antineoplastic chemotherapy regimen. Multiple intraindividual time point sampling will enable intrasubject reporting schedules to be constructed. Quantitative analyses will focus on data from each separate group, as well as comparisons among animal groups using analysis of variance (ANOVA). To characterize temporal patterns in plasma levels, cosinor analysis is planned; individual human cortisol levels and GI sensations will be examined separately for intraindividual patterns. The results will serve as a basis for hypothesis generation about enteral feedings which are often used with patient groups experiencing different delivery times, methods, kcal levels, or fiber contents.
| Westfall, U E (2000) How enteral feeding options influence corticosterone patterns in rats. Biol Res Nurs 1:233-44 |
